1. Field of the Invention
The present invention relates to a process for simultaneously producing carbon black and hydrogen.
2. Description of the Related Art
Hydrogen is a fundamental starting compound for use in the production of basic chemicals and, at the same time, an important form of primary energy.
At the present time, industrial hydrogen is mainly produced by steam reforming or partial oxidation of a carbonaceous feedstock, such as naphtha or natural gas.
For example, in steam reforming, a relatively light hydrocarbon feedstock, such as a gas oil of naphtha grade, a natural gas (methane), or an off-gas derived from petroleum refining (such as methane, propane, and butane), is reacted with steam under conditions of a pressure of 5 to 20 atm and a high temperature of 700 to 850.degree. C. over a catalyst according to the following formulae: EQU C.sub.n H.sub.2n+2 +nH.sub.2 O.increment.nCO+(2n+1) H.sub.2 EQU C.sub.n H.sub.2n+2 +2nH.sub.2 O.increment.nCO.sub.2 +(3n+1) H.sub.2 EQU CO+H.sub.2 O.increment.CO.sub.2 .increment.H.sub.2
to give a synthesis gas which is a mixture of carbon monoxide with carbon dioxide and hydrogen. In partial oxidation, a hydrocarbon is reacted with oxygen or air and steam under conditions of a pressure of atmospheric pressure to 50 atm and a temperature of about 1300.degree. C. to give a synthesis gas which is a mixture of hydrogen with carbon monoxide and the like.
On the other hand, carbon black is used as a filler, a pigment and the like. It is produced by instantaneously carbonizing a hydrocarbon feedstock at a high temperature of 300 to 1800.degree. C. within several milliseconds to form black fine particles with diameters ranging from 7 to 500 nm. Production processes used for this purpose include a furnace process, a channel process, an acetylene process, a thermal process and a lamp process. The features of these processes are summarized in Table 1.
TABLE 1 __________________________________________________________________________ Production process Features Feedstock __________________________________________________________________________ Furnace process A preheated feedstock is introduced in a turbulent Coal-derived or flow state into a furnace heated to about 1500.degree. C. petroleum-derived heavy cause instantaneous thermal decomposition, fuel oil immediately after which the resultant spray is cooled with water and filtered to collect carbon black. Channel process A partially burned, small diffusional flame is Natural gas or coal gas brought into contact with the bottom of a cooled channel steel to collect carbon black. Acetylene process Acetylene gas is continuously subjected to thermal Acetylene gas decomposition at about 1800.degree. C., and the resultant carbon black is separated and collected in the same manner as described above in connection with the furnace process. Thermal process A discontinuous system wherein natural gas is Natural gas thermally decomposed in the absence of air and any flame. Lamp process A feedstock is directly burned in a closed space, Coal-derived or followed by settling and separation to collect petroleum-derived oil, black. animal or vegetable oil __________________________________________________________________________
The above conventional processes for producing hydrogen are based on a reaction under high temperature and high pressure conditions and, hence, cost ineffective. Further, the use of steam and oxygen poses a problem of the occurrence of toxic carbon monoxide and carbon dioxide causative of global warming. The conventional processes for producing carbon black require a high reaction temperature of 1200 to 1800.degree. C. due to the utilization of thermal decomposition or incomplete combustion of natural gas or acetylene gas and, hence, are disadvantageously high in cost.